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Conference Proceedings
Differences And Similarities In Fatigue Failure Mechanisms Of Pa12 Pipe Grades Compared To Modern Pe Pipe Grades
Polyamide 12 (PA12) has been successfully introduced as material for SDR 11 gas piping systems up to 18 bar, representing itself as an attractive alternative to steel pipes for high-pressure applications. Practical experience and studies have confirmed excellent resistance against relevant pipe failure mechanisms such as slow crack growth (SCG) as well as any third-party attack or external surface damages (i.e. indentation effects of stones in the soil). Four different PA12 materials with varying macromolecular structure were investigated within the current paper. On the one hand, a major focus was put on the general applicability of the Cyclic Cracked Round Bar (CRB) Test as fracture mechanical approach to provoke quasi-brittle failure. On the other hand, the influence of the molecular weight MW, expressed by the relative viscosity number VNrel for PA12 grades, on the fracture mechanical failure behavior of PA12 grades and three different PE100 grades of increasing molecular weights was examined. Additionally, a fundamental comparison between PA12 and typical PE80, PE100 and PE100RC pipe grades in terms of long-term properties and relevant failure mechanisms was undertaken. The results demonstrate that the Cyclic CRB Test is a suitable method to provoke real SCG, and that the average molecular mass has a considerable influence on the SCG resistance of PA12 as it is the case for PE. Furthermore, findings of this paper outline an extraordinary SCG resistance for high-viscous PA12 pipe grades, which is exceeding typical toughness values of PE100RC by at least a magnitude at comparable stress levels and further confirm a high suitability for pipe installation techniques without sand beddings.
Performance Analysis Of Five Plasticating Screws
Three multi-channel “fractal” screws are compared with
general-purpose and barrier screws using an instrumented
single screw extruder for HIPS and LDPE at varying screw
speeds. Cold screw freezing experiments were performed
for all five screws with 5% black, blue, and violet colorants
serially added to neat HIPS. The cold screw pulls showed
that the general-purpose and barrier screws exhibited
significant racing of the materials within their screw
channels and, thus, broad residence time distributions.
Examination of the material cross-sections indicated
persistent coiled sheet morphologies which were best
dispersed with the third fractal screw.
Online Film Casting Of Pc/Mwnt Composites Using Ultrasound Assisted Twin Screw Extruder
The online ultrasonic film casting process to manufacture nanocomposite films was developed. In this process, polycarbonate (PC) of two different molecular weights was mixed with carbon nanotubes (CNT) and cast into films. Due to the relatively lower viscosity of low molecular weight PC (LPC) than that of high molecular weight PC (HPC), the torque of extruder and the die pressure of LPC was lower than those of HPC. The necking phenomenon during film casting of composites was investigated. It was found that at the same processing conditions, the film width of HPC was larger than that of LPC. The necking along film line decreased with increasing CNT concentration and imposition of ultrasound. This indicated that incorporation of the rigid CNT and imposition of ultrasound restrained the elongational flow behavior of melt, resulting in film of a larger width. The stress-strain behavior of composite films indicated that the incorporation of CNT improved the yield stress and decreased the elongation at break of the composite films. The light transmittance of the films continuously decreased with increasing CNT concentration.
Effects Of Post-Mixing Time And Dispensing Methods On The Dual Curability Of A Two-Part Acrylate-Epoxy Hybrid Adhesive System
The dual UV and ultimate thermal curability of a model, two-part acrylate-epoxy hybrid adhesive system and relevant governing factors are investigated by using dynamic rheometric and calorimetric techniques. Raw adhesive mixture samples were prepared with using the same static mixer, but via two different sampling methods (i.e. sequential and concurrent). The UV curability and ultimate thermal curability of mixture samples were measured in terms of heat of photo-induced cure reactions and ultimate glass transition temperature by using a differential scanning colorimeter (DSC) with and without the inclusion of a photocalorimeter accessory (PCA), respectively. In addition, the time-evolving viscosity of a fresh adhesive mixture sample was probed as a function of post-mixing time in small-amplitude oscillatory shear (SAOS) mode under ambient condition by using a dynamic rheometer, and is then correlated with the measured results of dual curability. Accordingly, the proper UV cure condition and pot life relevant to each of two different dispensing methods are determined based on practical optimization of UV curability and ultimate thermal curability of the hybrid adhesive system. The findings from the present study would provide some practical knowledge for advanced process development of similar acrylate-epoxy hybrid adhesive systems.
Understanding Scratch And Mar Behaviors Of Textured Polymer Surfaces Through Fem Modeling
Surface damages, such as scratch and mar, can significantly affect the aesthetics of polymer surfaces. Understanding the scratch and mar behaviors of polymer is more challenging if the surface is textured. Scratch and mar can be easily detected when the surface is smooth, whereas surface texture may hide the scratches. Introduction of texture to polymer surfaces has been shown to improve scratch visibility resistance; however, it also exposes polymers to new form of surface damages. In this study, a method of transferring actual surface texture characteristics into a finite element method (FEM) model is presented for realistic simulation of polymer scratch and mar behaviors. Influence of texture on scratch and mar behaviors is investigated through analysis of stress and strain field development. Implications of the numerical findings on scratch and mar visibility resistance are discussed.
Influence Of Meltspinning Conditions On The Morphology And Crystallization Of Polyester Fibers
Polyester, as a highly versatile polymer with desired physical and mechanical properties, conforms a major share in the synthetic fibers market. This article investigates the effect of meltspinning conditions on the morphology and thermophysical properties of a commercial bottle-grade amorphous copolyester in comparison with a semi-crystalline homopolymer polyester. After being molten in an extruder and exiting the die, polyester extrudates were drawn using a custom-made rotating drum at high speeds up to 1000m/min to form thin meltspun filaments. Microscopic images show the decrease in the diameter of fibers with increase in the drawing speed and temperature. Between two polyesters the homopolymer shows a more significant attenuation with the average fiber diameter down to 25.2 µm (equivalent to the diameter decrease of about 140 times or the drawing ratio of above 19,000 times) for the drawing speed of 1000m/min and at 260°C. Cohesively, differential scanning calorimetry shows a lower cold crystallization temperature for the homopolymer polyester, pointing to its higher crystallization kinetic, which can be attributed to a higher degree of chain orientation in this polymer. In a similar way, increase in the drawing speed and decrease in meltspinning temperature for both polyesters results in their decreased cold crystallization temperature, as a sign of their increased molecular chain orientation. Upon annealing the meltspun fibers at 200°C for 20min the cold crystallization peak vanishes to confirm their significant increase in the crystallization degrees. Both polyesters, particularly upon being annealed, show increase in the degree of crystallinity with increase in the drawing speed and decrease in the meltspinning temperature.
Fracture Properties Of Polyolefin Recyclate Formulations
A high utilization of polymeric recyclates must be considered to achieve current and future policy goals for a circular economy. Therefore, recyclate formulations will have to meet the application specific performance requirements in order to substitute virgin materials. In this research, four commercially available polyolefin recyclate grades were characterized with analytical and mechanical methods. Furthermore, as a highly accelerated technique to characterize long-term mechanical performance, fatigue crack growth experiments were conducted. In all recyclates, contaminations of foreign particles were found and impair the mechanical properties as well as fatigue crack growth behavior. Nevertheless, the experiments point out clear differences and allow for a distinct ranking of the recylates in terms of fatigue crack growth resistance.
Flow Behavior And Polymer-Particle-Interaction In Highly Filled Polylactides
Adding fillers to polymers allows highly functional materials and thereby properties like electrical conductivity that are not achievable by polymers themselves. But higher amounts of fillers cause an increase in viscosity and thus a change in flow behavior which in turn induces difficulties in plastic processing. Above a certain value (percolation threshold) there is a flow restriction which has to be overcome by a higher pressure in plastic processing. Besides the amount of filler the flow behavior of highly filled polymers depends on the filler itself and its particle shape. Especially the aspect ratio plays an important role. Another important factor is the combination of the polymer and the filler and whether there are any interactions between each other. By differing the amorphous phase of polymers into a rigid amorphous and a mobile amorphous fraction, predictions about interactions are possible. The objective is the generation of such a flow restriction and the combined investigation of a polymer-particle-interaction. Polylactide (PLA) was used as matrix whereas minerals were used as filler material in different amounts up to 50 vol.-%. SiO2 was chosen because it is available in different spherical sizes and clay because of its platelet geometry. Rheological investigations were done on a plate-plate rheometer while the interactions were investigated using differential scanning calorimetry. The results show that a higher aspect ratio leads to a faster increase in viscosity achieving the rheological threshold. As a result of the caloric investigations the highly filled plastics show only a minor interaction between polymer chains and filler surface. This leads to the conclusion that the change in flow behavior is mainly caused by a direct interaction between the particles.
Mechanical Properties Of Polyacrylonitrile Nascent Fibers Prepared By Super-Large Length-Diameter Ratio Twin-Screw Extruder With Different Screw Speed
Polyacrylonitrile(PAN)-based carbon fiber is widely
used in our daily life. Due to the increased demand for
carbon fiber, the production capacity of PAN fiber is in
urgent need to be improved. Twin-screw extrusion (TSE)
is a general method for producing PAN fiber. In this paper,
PAN nascent fibers were prepared by a self-developed
super-large length-diameter ratio twin-screw extruder. The
effect of screw speed on the initial residence time and
mechanical properties of PAN fibers was investigated. The
results showed that as the screw speed increases, the tensile
strength tends to decrease.
Residence Time Distribution In Solid-State Shear Pulverization (Sssp) Extruder
Solid-state shear pulverization (SSSP) is a twin screw extruder-based processing methodology that has been developed and applied to a wide range of polymer-based materials over the last 20 years. Detailed processing-structure-processing relationships can be realized when the complex interplay between the numerous operating parameters of SSSP can be consolidated through universal processing parameters. One such parameter, residence time distribution, is the focus of this paper; tracer pulse experiments are conducted for a range of SSSP operating conditions, and important characteristics and trends are extracted towards a better understanding of the SSSP process.
Reaction Injection Molding Of Polyurethane Medical Device Components
Polyurethanes (PU) are widely used in the medical device industry due to their desirable combination of biological compatibility and stability, mechanical durability and processability [1-4]. Components forming a medical device are often small in dimension and intricate in structure, and a common operation in medical device manufacturing is the bonding of different device components to each other or an additional substrate. The manufacture and assembly of these intricate device components requires complex molds and molding methods. The bonding operations can be achieved via a number of methods, including welding processes, adhesive bonding, and thermoplastic reflow. However, these methods have limitations on bond strength and stability, and frequently require the introduction of a new material into the device. In this paper, we examine the potential to use and optimize reaction injection molding of medical PUs to create an intricate part and a bond between multiple components in a medical device.
Improved Performance Of Polyurethane Foam Insulation Using Polylactide Biopolymer Liners And Its Impact On Energy Efficiency Of Refrigerator And Freezers
This paper compares the effect of constant-temperature aging on the thermal conductivity of polyurethane foam in simulated refrigerator panels made from polylactic acid biopolymer from NatureWorks (Ingeo®) and high-impact polystyrene. Specimens were aged at room temperature and thermal conductivity measurements were made at 10°C over a period of 2.4 years. The energy use over the life of refrigerator and freezer is also calculated using the Energy-Efficient Refrigerator Analysis program developed by the United States Department of Energy to estimate the energy savings potential of various technology option upgrades (cabinet and refrigeration system) for rulemaking purposes. The results show that energy savings from implementing the Ingeo liner range from 818 to 1395 kWh (7.3 to 12.5% of total energy use) over a 15-year period.
Pyrolyzed Soybean Hulls As Fillers In Polypropylene And Linear Low Density Polyethylene
Pyrolyzed (450 and 500oC for 4 minutes) Soybean Hulls (PSBH) were used in as-received and ballmilled conditions as filler in Linear Low Density Polyethylene (LLDPE) and Polypropylene (PP) to evaluate mechanical behaviors for composites of PP/PSBH and LLDPE/PSBH. While the as received PSBH particles varied in size considerably with size going up to 710 μm for about 52% of the particles, and larger for the rest, the mechanical properties did not change substantially when as received PSBH was ball milled down to 10 μm or smaller size, except for maximum strain values for the LLDPE/PSBH composite. Elastic modulus of PP/PSBH increased with increasing PSBH amount. Elastic modulus and maximum stress values for LLDPE/PSBH increased with increasing amount of PSBH filler. When the trends of the elastic moduli for PP/PSBH and LLDPE/PSBH composites were compared, the effect of PSBH filler amount was found to be similar on both composites, resulting in increasing behavior for the elastic moduli in similar proportions. In the case of strain values at maximum stress, PSBH addition affected LLDPE more than PP with higher amounts of strain reduction. The maximum stress values presented opposite behaviors with those for LLDPE increasing while those for PP decreasing. At the highest PSBH amount added (50 %wt.) the maximum stress and the corresponding strain values for both LLDPE/PSBH and PP/PSBH composites became very close when using as-received filler. Our results also showed that pyrolysis of SBH at 450 and 500oC for 4 min resulted in significantly higher reductions in feed-stock weight and higher values in carbon content in comparison to pyrolysis at 275 and 325oC, which correspond to typical torrefaction temperatures.
Quality Index Design For Online Monitoring Injection Molding Process
Quality control is a crucial issue in the injection molding process with target of obtaining a high yield rate and reducing production cost. However, conventional injection molding acts like a black-box in which the flowing behavior of polymer melt within cavities is unseen, and the tuning of process parameters is heavily relied on operators' experience, design of experimental methods, or even trial-and-error. Such approaches are not only time-consuming but also lack of assuring consistent injection molding qualities and quality control is then required. Nowadays with the advance of sensing technology, many sensors are available to detect the flowing behavior of polymer melt within mold cavities. Particularly the pressure, velocity, and temperature that affect the flowing ability of polymer melt can be detected in time. In other words, injection molding now has been transformed into a grey-box and a scientific viewpoint to tune process parameters can be realized. In this research, a quality index extracted from pressure profile is aimed for online quality monitoring. In addition, the clamping force increment quality index extracted from the tie-bar elongation which is detected by strain gauges attached on tie bars, free of invading injection mold structure, is paid much attention. To verify the feasibility of the designed quality index using to prediction the injection molded quality, varying barrel temperature, back pressure and rotational speed of plasticizing screw those can affect the plasticizing quality of raw materials are conducted in this investigation. Experimental results reveals that the clamping force increment as well as pressure peak index extracted from injection system pressure, nozzle pressure, end-of-filling cavity pressure profiles during injection molding are highly correlated with injection-molded qualities and thereby are feasible to be a good quality indicator.
Role Of Polyamide 6 As The Antishrinkage Agent In Pa 6/Pebax Blends
Polyether block amide (PEBAX) is a thermoplastic elastomer (TPE) known for possessing high impact resistance and significant flexibility over a wide range of temperatures. The foaming ability of PEBAX was investigated by batch foaming using CO2 as the blowing agent. Because the tensile modulus of TPE is low, TPE usually shrinks right after foaming.
In this study, polyamide 6 (PA 6) and styrene maleic anhydride (SMA) were blended with PEBAX to reduce foam shrinkage. The results indicated that SMA and PA 6 help in reducing foam shrinkage. The microstructure images showed that cell density increased and the cell size decreased after these antishrinkage agents were added.
Determination Of The Barrel Temperature Setting Of Single Screw Extruders Using Fuzzy Logic
In this article, a self-optimizing approach using fuzzy logic to determine the correct barrel temperature setting of single screw extruders is presented. After quantifying characteristic values to measure the polymer melt quality, experimental investigates were carried out. The experimental investigations contribute to the acquisition of process knowledge thus to the development of a knowledge database. The results of the experiments clearly demonstrated the improvement of the material and thermal melt quality by changing the barrel temperature setting. By applying fuzzy set theory, imprecise or vague knowledge can be included into a model that can be mathematically displayed, too. Furthermore, the description of linguistic variables using fuzzy sets can be used to construct an expert system that adequately processes qualitative information. Therefore, a fuzzy logic based algorithm was developed for setting the barrel temperature setting autonomously. Through the experimental results, the proposed fuzzy algorithm has been shown to be powerful under laboratory conditions. Moreover, the fuzzy controller is shown to be useful since the determination of a barrel temperature setting within the desired melt homogeneity independently of the machine operator or trial and error experiments.
The Effect Of Graphene Nanoplatelets On The Complex Viscocity Of High Density Polyethylene
In this paper, we investigated the rheological properties of high density polyethylene (HDPE) based composites filled with different amounts of graphene nanoplatelets. The composites samples were prepared in the form of films by the method of melt mixing. A parallel-plate rheometer was used to measure the rheology properties, including the complex viscosity, storage modulus and viscous modulus. The LVE range of all the samples was determined firstly, and then we studied the rheological properties of pure HDPE and graphene/HDPE composites. The effect of graphene content on the rheological properties of the graphene/HDPE composites at 150 °C was especially investigated. The results showed that the complex viscosity of the graphene/HDPE composites was decreased and then increased with increasing the content of graphene from 0.25 to 1.0wt%. However, increased graphene content did not exhibit distinct effect on storage modulus and viscous modulus of graphene/HDPE composites.
Determining The Degree Of Agglomeration Of Solid Additives While Using Inline Injection Molding Compounding (Iimc)
During the plasticization of polymers with fillers and reinforcing materials within the special process of inline injection molding compounding (IIMC), agglomerations of the additives cannot be excluded. The agglomerations lead to uncertain process management, which is why this study evaluates a process for rapid determination of agglomerates and degree of agglomeration for further development of the IIMC. In addition to the degree of agglomeration, the tensile strength was also investigated in order to detect a correlation between the determined parameters.
The Influence Of Different Die Geometries On The Extrusion Process Of High-Consistency Silicone Rubber
Silicone Rubber and especially High-Consistency Silicone Rubber (=HCR), are typically processed in the extrusion process. Due to the high requirements in terms of the material properties and the geometric dimensions, a fundamental knowledge of the whole process including experiences in tool design are essential. In this study, HCR with different Shore-hardnesses are extruded on a vertical silicone extrusion line with various breaker plates with different length to diameter ratios (=L/D-ratio) in order to analyze the influence on the whole extrusion process. It has been shown that soft materials, regardless of die geometry, achieve higher throughputs compared to harder compounds. Increasing counter pressure, e.g. due to longer die lengths, reduces the volume flow rate per revolution and reduces the throughput. Tools with a small L/D ratio achieve the highest throughput. With regard to die design, it can be seen that dies with a smaller L/D ratio have clear advantages: due to their short length, they represent a smaller pressure consumer. As a result, the dwell time in the extruder is shorter and the risk of scorch is reduced. The absolute value of the swelling behavior is larger, but can be predicted with high accuracy. Shorter tools also show less flow instabilities.
An Anomaly In The Drop Dart Testing Of Polyethylene Film
Drop Dart testing is one of a number of standard characterization techniques employed as a means to characterize film toughness. In this test, a dart with varying weights are dropped from a prescribed height on a film and the weight at which 50% of the tests penetrate the films is reported. It was found that friction between the dart head and the film can adversely affect the results in this test. Application of talc to the surface of the film prior to the test, thus reducing friction between the dart head and the film, improved results significantly in metallocene catalyzed linear low density polyethylene films. The addition of slip and antiblock often resulted in significant improvement as well. These results call into question the utility of the test as it is presently implemented to measure true, intrinsic film toughness. On the other hand, if anomalous frictional effects were to be eliminated through the routine application of talc to the film surface, then the validity of the test can be restored.
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